[ Eq(Derivative(x1, t), (1*k1*k11 + (-1)*k2*x1*x6*1/1000 + (-2)*k3*x1*(x1 - 1)*1/2 + 2*k4*x2 + (-1)*k7*x1*x3**2/(k8**2 + x3**2) + 1*k5*x3)/k10),
  Eq(Derivative(x2, t), (1*k3*x1*(x1 - 1)*1/2 + (-1)*k4*x2 + (-2)*k6*x2*(x2 - 1)*1/2)/k10),
  Eq(Derivative(x3, t), (4*k6*x2*(x2 - 1)*1/2 + 1*k7*x1*x3**2/(k8**2 + x3**2) + (-1)*k5*x3)/k10),
  Eq(Derivative(x4, t), 0),
  Eq(Derivative(x5, t), 0),
  Eq(Derivative(x6, t), (-1)*k9*x6/k10) ]